Don't know why more research hasn't been done on Boron fusion. Since it gives off an electron you don't need any turbines or heavy equipment just a transformer. Instead we spend billions on H2 H3 fusion. Makes no sense to me.
We have yet to achieve the plasma densities, temperatures, and confinement levels to attain self-sustaining fusion with even D/T or D/D reactions. These are the lowest energy reactions, which is why we are pursuing them at the moment. D/He3 and p-B11 fusion are orders of magnitude harder to achieve. If we can't get D/T fusion past break-even we'll just be that much farther from getting p-B11 fusion to work too. As far as actual commercial fusion plants, such things may be dependent on more advanced fusion fuels and aneutronic reactions, but we are far from being capable of building even test reactors for such fuels.
except for D/T (and D/D), most of other fusion reactions which don't involve exotic components (like He3) don't seem to be confine-able by the mainstream magnetic confinement (tokamak). The inertial confinement is starting to come back and with it the promise of the other reactions.
the lowest upper bound we have is 5-10Kt thermonuclear bomb. I.e. we do know that using at least one type of confinement - inertial - with X rays as driver it is possible to get energy-net-positive on the scale of such a small bomb. On the other side, ie. the lower bound - the Z machine at Sandia is generating X rays with power enough to drive the reaction similar to how the fusion is driven by X rays in the H bomb, just on the much smaller scale, and we do know that scaling it up or the other existing designs, like the tokamak or polywell or laser driven device like NIF, does increase the reaction efficiency. Somewhere between is the practical energy-net-positive reactor. It can be order or 2 of magnitude bigger than ITER - well, the modern coal burning or nuclear plant is several orders of magnitudes bigger than the campfire of the cavemen where it started from.
